Volume 30, Issue 5

Addressing environmental degradation and ensuring environmental sustainability are inextricably linked to all methods of reducing volatile organic compounds (VOCs) from the environment. A packed column air stripper is a typical example of such technologies for the removal of VOCs from polluted water. The present review is devoted to the applications of a packed column air stripper and, in comparison with previous reviews, presents further elaborations and new information on topics such as modeling and simulation of the dynamic behavior of the air stripping process in a packed column air stripper. The paper observed that a knowledge gap still exists in the synthesis of this knowledge to formulate practically applicable mathematical relationships to describe the process generally. Therefore, further researches are still required in the area of air stripper performance optimization, particularly in the development of a mathematical model and the optimization of an air stripper using a statistical experimental design method. Such a determination is critical to the understanding of the interactive effect of process variables such as temperature, air-to-water (A/W) ratio, and height of packing on air stripper performance.

Fossil fuels are the major contributors to the emission of anthropogenic carbon dioxide (CO 2 ) to the atmosphere, rendering global warming a challenging issue to the researchers and industries. Although natural gas has been recommended as a clean fuel compared to other fossil fuels, geological sources of natural gas are not free of impurities. Economical commercialization of natural gas with high sour gas contents as well as facilitating the geosequestration of sour gases for enhanced oil recovery (EOR) need several environmentally sound and cost-effective gas separation methods. Moreover, stringent restrictions should be drawn to mitigate the unfettered greenhouse gas emissions to the atmosphere. In the present study, existing low-temperature conventional CO 2 capture methods, namely, cryogenic distillation process along with emerging nonconventional and hybrid methods, have been demonstrated. Also, the limitations and operational conditions during the application of these processes have been mentioned. The future prospects of the emerging technologies have been compared with conventional methods. Hybrid cryogenic distillation networks for multiproduct industrial production of different hydrocarbons and CO 2 products at higher pressures of 40 bar and above showed promising potentials. A concise classification and summary of innovative emerging technologies along with conventional methods has been presented in this paper for possible future commercial exploitation.

Chemical process industries (CPI) are usually home to a large number of complex systems and components required for various operations involving hazardous chemicals. The intense operating conditions and complex interactions between the systems make the chemical plants vulnerable to accidents. Quotidian incidents and mishaps can lead to catastrophic incidents. Thus, the area of risk assessment and reliability analysis in CPI has been of much interest to the research community. The complexity of processes in CPI demands a risk assessment tool that can adapt itself to the dynamic environment and can efficiently model the functional and sequential dependencies between the components and the effects of external factors, component degradation, and variation in operating conditions. The risk assessment tool must have applicability during the operational lifetime of the system to serve as a platform for decision making and risk management. The unavailability of empirical data for some variables is another pertinent issue in risk analysis and reliability assessment in CPI. Analysts often have to work with subjective information such as expert opinion. Bayesian statistical methods based on the Bayes theorem are considered by many to be an effective tool to address the above-mentioned issues. These methods are based on the subjective interpretation of probability that helps to model the epistemic uncertainties and easily propagates them through complex system models. The methods provide a formal systematic way to incorporate subjective information into calculations. The inherent updating property accoutres these methods with the ability to deal with real-time changes. The opponents, however, point out that the methods produce high overconfidence and randomness in computed answers. In the last two decades, an increased interest can be seen in the research community toward the use of Bayesian methods in risk assessment. This paper presents a comprehensive literature review of the application of Bayesian methods through Bayesian parameter estimation techniques and Bayesian updating procedures in process industries. Both these techniques have been extensively used in various aspects of risk analysis, which are very pertinent in CPI. The purpose of the study is to produce an effective reference guide for scholars interested in applying Bayesian techniques to risk and reliability assessment in CPI.

Polyampholytes are charged macromolecules bearing both anionic and cationic groups along the polymer backbone. Polyampholytes can be synthesized by classic and controlled free radical polymerization, anionic polymerization, and group transfer polymerization (GTP). The aqueous solution behavior of polyampholytes is dictated by columbic interactions between the basic and acidic residues. Polyampholytes show both polyelectrolyte and anti-polyelectrolyte behavior in aqueous media. Factors such as charge density, charge asymmetry (i.e., degree of charge balance), charge spacing and distribution, substrate surface charge, structural conformation, and solution ionic strength are critical parameters. Polyampholytes are interesting for numerous reasons and are used for many technology processes such as water treatment, enhanced oil recovery (EOR), sludge dewatering, papermaking, pigment retention, mineral processing, and flocculation. In the present study, the main structural features, behaviors, mechanisms of interaction, and recent field applications of polyacrylamide (PAM)-based polyampholytes are reviewed.

Research in the use of phase change materials for buildings has successfully shown that use of phase change materials results in savings and the environmentally benign use of premium energy. Research work in thermal comfort using phase change materials needs to be more compatible with other building materials. This article reviews the preparation and utilization of various organic phase change materials investigated by researchers for thermal comfort in buildings. The effect of mixing of different phase change materials and ensuing chemical processes on the melting point and latent heat was reviewed.